The present disclosure is directed to a grounding clip for a hybrid composite/metallic guide vane of a gas turbine engine.
Certain gas turbine engines include guide vanes made from organic matrix composite materials. These guide vanes can include a metallic sheath located at the leading edge of the guide vane. The metallic sheath functions to protect the composite materials of the guide vane. The composite guide vane and the metallic sheath can be attached to a guide vane attachment fitting to secure the vanes. The attachment fittings are located on either end of the guide vane. The attachment fittings are metallic.
Current designs utilize a metallic through-bolt that extends between the guide vane and the metallic attachment fitting to secure the guide vane. An adhesive is also utilized to secure the guide vane to the attachment fitting.
A grounding path is required to enable static electricity generated by airflow over the guide vane to discharge to the engine, or to allow for a grounding path in the event of lightning strike on an engine.
In order to properly function to conduct the electricity, the through-bolt relies on intimate electrical contact between the metallic attachment fitting and the through-bolt. The path of conduction can include flowing through the through-bolt to either the composite fibers themselves or to an embedded grounding strap within the composite vane, to make the electrical connection which provides the ground path. Other options for grounding the guide vane and metallic sheath can include coupling a jumper cable to the metallic sheath at the leading edge of the composite vane to the metallic fitting. The jumper cable can adversely affect aerodynamics, since it is exterior to the attachment fitting and exposed to the working fluid of the guide vane.
The presence of the adhesive between the guide vane and the metallic attachment fitting, as well as the gapping required to ensure the two pieces fit together, create difficult challenged for a design to have intimate contact along the sides of the guide vane and the attachment fitting. This inherent structure creates a problem for obtaining a robust electrical grounding path for the composite matrix guide vanes with the metallic sheath and metallic attachment fitting.
What is needed is a robust attachment scheme that includes an intimate electrical contact bridging the gaps between the guide vane, metallic sheath and metallic attachment fitting.